Researchers there have identified an enzyme with a key role in the biological manufacture of glycyrrhizin, a sweetener- up to 300 times more potent than sugar- from licorice root, which could enable industrial production of the "natural" sweetener by genetically modified plants or microbes.

Because of its sugary taste, glycyrrhizin is used worldwide as a natural sweetener and flavouring additive, so the efforts to pick the wild root are worth around 40 million US dollars.

But licorice production is dependent on the collection of wild Glycyrrhiza plants, especially in China, and this has caused a decrease in licorice reserves and an increase in desertification where it is harvested.

Now Prof Toshiya Muranaka of Yokohama City University has found an enzyme in licorice that catalyses a key step in the synthesis of glycyrrhizin.

The result could enable industrial production of the sweetener by genetically modified plants or microbes, containing the enzyme.

In the study, published in the Proceedings of the National Academy of Sciences, his team shows that genetically modified yeast with one gene can make a large amount of glycyrrhizin intermediate. However, another three would be needed for the microbe to make the sweetener.

The chemical glycyrrhizin is thought to have various medical properties, including anti- inflammatory, immunomodulatory, antiulcer, and antiallergy effects. In Japan, it is used to help protect the liver of patients with hepatitis.